OREGON STATE UNIVERSITY

Glossary beginning with L

Volcano Term Definitions

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Laccolith

A body of igneous rocks with a flat bottom and domed top. It is parallel to the layers above and below it.

Lahar

A torrential flow of water-saturated volcanic debris down the slope of a volcano in response to gravity. A type of mudflow.

Lapilli

Literally "little stones." Round to angular rock fragments, measuring 1/10 inch to 2 1/2 inches in diameter, which may be ejected in either a solid or molten state.

Lava

Magma which has reached the surface through a volcanic eruption. The term is most commonly applied to streams of liquid rock that flow from a crater or fissure. It also refers to cooled and solidified rock.

Lava Flow

An outpouring of lava onto the land surface from a vent or fissure. Also, a solidified tongue like or sheet-like body formed by outpouring lava.

Lava Lake

A lake of molten lava, usually basaltic, contained in a vent, crater, or broad depression of a shield volcano.

Lava Tube

A tunnel formed when the surface of a lava flow cools and solidifies while the still-molten interior flows through and drains away.

Lithic

Of or pertaining to stone.

Lithosphere

The rigid crust and uppermost mantle of the earth. Thickness is on the order of 60 miles (100 km). Stronger than the underlying asthenosphere.

Luster

The reflection of light from the surface of a mineral.